Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

This is the description's strongest contribution: with readOnlyHint=true on a tool named 'update_*', the text resolves the apparent tension by explaining it only returns instructions and opens nothing itself, and routes execution to cotlet_browser_* tools. It stops short of describing authentication needs, what the returned steps look like in structure, or whether the guide is account-specific.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three sentences, front-loaded with the action and immediately followed by the crucial clarification that it does not act. The trailing sentence about Intervals.icu having a public REST API is tangential, does not explain why it matters, and carries an oddly future-dated check timestamp, so it is wasted space.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a zero-parameter, no-output-schema, read-only guide tool, the description supplies the necessary shape: what it returns (steps with screens, buttons, fields) and what to do next (browser tools). It is only slightly incomplete in not stating what preconditions, if any, the browser session must satisfy.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Zero input parameters, so there is nothing for the description to disambiguate and the baseline of 4 applies. One residual gap is that it never explains how the target activity, note text, or RPE value are conveyed to the browser tools downstream.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

Names a specific verb and resource (update activity notes and RPE) plus the account scope (the user's own Intervals.icu account). It also reveals the non-obvious actual behavior — that the tool returns step-by-step guidance rather than performing the update — which is essential for distinguishing it from a true mutation tool, though it does not contrast itself with close siblings like intervals_icu_comment_on_an_activity.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Implies the workflow clearly: call this to get instructions, then perform the action with cotlet_browser_* tools in the user's Cloud Browser, and states it 'opens nothing by itself'. However, it gives no explicit when-not-to-use guidance and never names an alternative tool for the same outcome (e.g., a direct API-based update or the comment tool).

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.